1. CCleaner
CCleaner (Crap Cleaner) is without doubt the best and the most popular tool for Windows optimization and cleanup. It consists of almost all the modules for optimizing and cleaning Windows including a registry cleaner, an uninstaller and temporary files cleaner with a plethora of options which includes cleaning the history and temporary files for most of the popular programs including Internet Explorer, Mozilla Firefox, Opera, Safari, Google Chrome, Adobe products, Microsoft Office and a lot of others. CCleaner includes an option to take a backup of system settings before proceeding with the cleaning and optimization process. This enables you to easily restore everything to its original state if anything goes wrong. It also includes a drive wiper which can securely erase the contents of any drive and make it irrecoverable. The down side of CCleaner is that some options like adding the CCleaner option to the Recycle bin, check for updates automatically etc. are already checked during installation. I think it should be up to the user to select them if he needs to.
2. FCleaner
FCleaner is a very close competitor to CCleaner. I like the graphical user interface of FCleaner as it is easier to use than CCleaner because it uses a three dimensional menu approach. The uninstaller module of FCleaner is far more advanced and offers to repair or remove a software in addition to the traditional uninstallation methods. It also includes a startup manager for optimizing and cleaning Windows startup. Another feature that I like is RAMRush. Windows does a pretty good job in optimizing the usage of memory but there are applications which will leak some memory which makes it unusable. RAMRush does the job of cleaning those patches of memory leaked by running programs.
3. Glary Utilities
Glary Utilities is another software to keep Windows in good shape. While it has features very similar to the above given utilities, it becomes superior to both of them by offering one additional feature, the 1-click maintenance. You can just click the 1-click maintenance button to analyze the system for problems. The modules consist of registry cleaner, shortcuts fixer, startup manager, temporary files cleaner, tracks eraser and spyware remover. Glary Utilities will automatically create a system restore point before proceeding to the cleanup and optimization process. If you feel anything has gone wrong, you can easily restore you system to the previous state. The down side of Glary Utilities is that it offers to install the Ask.com toolbar during installation and this option is checked by default.
More Alternatives
While the above mentioned software are the best and the most used free tools for optimization, there are others worth mentioning: WinUtilities is a close competitor to Glary Utilities with almost all the same functionality including 1-click maintenance. SlimCleaner includes some additional features to the traditional ones like file shredder, hijack log etc. SKTools Lite is specifically made for smartphones having Windows Phone Operating System. Please note that you should always backup your registry before running any of these tools as these tools can cause some of the programs to malfunction. This is very rare and I have never seen any adverse effects but care should always be taken in this regard. What do you use to keep your Windows in shape? Tell us your choice through comments.